Colorimetric testing of all kinds of fluids from water to blood has long been a standard method of chemical testing. Inexpensive colorimetric test kits have been made for testing swimming pool water and for the smaller but more demanding aquarium hobby. In the aquarium hobby colorimetry is used to test water not only for chlorine and pH (i.e. acidity) but also for ammonia, phosphate, carbonates, copper, and other properties, impurities, and pollutants. But aquarium test kits have mostly comprised nothing more than a box containing one or two small dropper bottles of reagents, one or two sampler vials, and color patches printed on an opaque instruction card. With the growth of the even smaller but more demanding saltwater aquarium hobby it became obvious that attempting to match the color of light transmitted through colored water to the color of light reflected from opaque color patches printed on paper was crudely inadequate. A notable attempt to provide a more adequate colorimeter and set of test kits was made in Germany and sold here under the name Tetra Test. It proved to be much too expensive for wide acceptance in the aquarium hobby and it was too elaborate for the swimming pool industry.
In the German "Tetra Test" set of test kits the colorimeter comprised a plastic holder into which two specially designed rectangular sampler vials could be inserted and a color wheel mounted. Each color wheel comprised a plastic disc with a ring of non-opaque colored plastic chips to present a selectable color window. The plastic holder held one sampler vial behind the color wheel with the other sampler vial adjacent to it. The water in the sampler vial behind the color wheel was left untreated and it served to correct the window color to compensate for any initial coloration in the water being tested. Reagents were added to the water sample in the adjacent vial and the color that developed was compared to the color windows which were brought into position in front of the untreated vial by turning the color wheel. While this made an excellent colorimeter in principle, it was too expensive partly because the small market to which it was addressed could not justify the capital investment for the required tooling. It also was and is practically impossible to accurately control the color of plastic chips except at prohibitive cost. Accordingly it is an object of my invention to drastically reduce these sources of cost by using readily available commercial components and materials in a colorimeter test kit apparatus that is equal or superior to the "Tetra Test" system in principle and in performance. Other objects and advantages of my colorimeter test kit apparatus and method are described in the summary or will be obvious to those skilled in the art.
Colorimetric test kits have also been adapted to the aquarium hobby with a standard form of colorimeter found in professional laboratories. The colorimeter consists of so-called Nessler Tubes mounted in a plastic holder into which a sampler vial can be inserted for color comparison. Nessler Tubes are glass tubes filled with colored water. A Nessler Tube colorimeter is therefore bulky, expensive, and subject to breakage. For the aquarium hobby such colorimeters are commonly limited to no more than two or three Nessler Tubes in an effort to minimize costs. Even then they are still too expensive, and too bulky, to have found wide acceptance in the aquarium hobby. Since the aquarist is faced with the need to test for many different things he requires many test kits, and a set of bulky test kits is obviously unattractive and inconvenient. Nessler Tube test kits and the "Tetra Test" system overcome the inadequacy of the opaque color patches in cheap kits by providing a better colorimeter but they do not solve other problems. They still consist of one or two dropper bottles of reagents, with sampler vials, and they are bulkier than ever because of the addition a colorimeter apparatus in place of the cheap color patch card. They also retain the problem that dropper bottles are unsuited to holding some of the more volatile reagents which easily evaporate. It is an object of my invention to provide a test kit made of commercially available parts that cooperate to eliminate many problems including the bulkiness and the use of unsealable dropper bottles, while at the same time providing a true colorimeter with color windows and automatic color compensation.